Preparation, Structures and Optical Properties of [H3N(CH2)6NH3]BiX5 (X=I, Cl) and [H3N(CH2)6NH3]SbX5 (X=I, Br)

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1 Notizen 927 Preparation, Structures and Optical Properties of [H3N(CH2)6NH3]BiX5 (X=I, Cl) and [H3N(CH2)6NH3]SbX5 (X=I, Br) G. A. M ousdis3, G. C. Papavassiliou3 *, A. Terzisb, C. P. R aptopouloub 3 Theoretical and Physical Chemistry Institute, N ational H ellenic Research Foundation, 48, Vassileos C onstantinou Ave., A thens 116/35, G reece b Institute of M aterials Science, NCSR, Dem okritos, A thens 153/10, Greece Z. N aturforsch. 53b, (1998); received M arch 2, 1998 A lkylam m onium H alogenobism uthates and A ntim onates, Excitonic Spectra, Dielectric Properties The preparation, crystal structures and optical absorption spectra of [H3N(CH:>)6N H 3]BiX5 (X= I, Cl) and [H3N (C H 2)6N H 3]SbX5 (X=I, Br) are reported. The anions of the com pounds consist of M X6-octahedra (M=Bi, Sb) sharing cis vertices in one-dim ensional zig-zag chains. Because of their one-dim ensional character, a blue shift of the excitonic absorption bands, in com parison to those of higher dim ensionality systems (M X3), is observed. Introduction C om pounds of the type (A )xmyxz (where A is am ine-h + or l/2diam ine-2h +; M= Bi, Sb, Pb, Sn, etc; X=I, Br, Cl) have been known for a long time [1-10]. Also, alkylbismuth diiodides have been prepared recently [11]. Most of these com pounds are low-dim ensional (LD ) semiconducting m aterials, in which the inorganic com ponent is the active p art of the system (sem iconductor), while the o r ganic com ponent plays the role of the barrier (for a review see [10]). Because of their low dim ensionality these m aterials are candidates for the preparation of electronic and optoelectronic devices [10]. The alkylam m onium halogenantim onates and bism uthates crystallize in a num ber of different stoichiom etries of which the most common are A M X 4, A 2M X5, A 3M 2X9, and A 3M X6. They contain an anionic sublattice built of distorted M X63- octahedra, isolated (0D) or connected with each * R eprint request to Prof. G. C. Papavassiliou. other via bridging halogen atoms, forming chains (ID ) or layers (2D) separated by the ammonium cations. Thus, these com pounds are natural quantum -dots, -wires or -wells, respectively. By decreasing the dim ensionality, the low energy optical absorption peaks, due to the lowest free-excitonic states, are shifted to higher energies (i.e., to shorter wavelengths). The intensity of excitonic optical absorption peaks of LD systems is higher than that of the corresponding three-dim ensional systems (3D). In o ther words, the excitonic binding energy and oscillator strength of LD systems are increased, in com parison to those of 3D systems [10]. Recently, the optical absorption bands arising from the excitonic states of com pounds A 3M 2X9 and A 3M X 6 have been investigated [2-4], H ow ever, little is known about the A 2M X5 compounds, which usually are ID systems [5,6]. In this paper we report the preparation and characterization of the (ID ) com pounds [H 3N (C H 2)6N H 3]M X, (M= Bi, X=I, Cl; M=Sb, X=I, Br). Experimental Starting m aterials and apparatus The following starting m aterials were used w ithout further purification. (B i0 )2C 0 3 (Aldrich 27,894-7), Sb20 3 (Ferak 30199), hydroiodic acid, 57% (M erck 341), hydrobrom ic acid 47% (M erck 304), hydrochloric acid 25% (M erck 312), 1,2 D iam ino hexane (Fluka 33000). Crystal X-ray intensity data were collected on a Crystal Logic [12] dual goniom eter using graphitem onochrom ated M oka radiation. U nit cell dim ensions were determ ined and refined by using the angular setting of 24 autom atically centered reflections in the range 11 <20<24. Intensity data were recorded using a 6-26 scan: for [H3N (C H 2)6N H 3]BiI5, 6 range = 0-25, scan speed 3 m in-1, scan range 2.4 plus a xa 2 separation, data collected/unique/used 3313; for [H3N (C H 2)6N H 3]BiCl5, 6 range = , scan speed 1.5 min_1, scan range 2.1 plus a xa 2 separation, data collected/unique 4379/4237(/?int = ), data used 4092; for [H 3N (C H 2)6N H 3]SbI5, 6 range = 0-25, scan speed 2.2 min_1, scan range 2.4 plus a xa 2 separation, data collected/ unique/used 3255; for [H3N (C H 2)6N H 3]SbBr5, 6 range = , scan speed 1.5 min-1, scan /98/ $ Verlag der Zeitschrift für Naturforschung. All rights reserved. D Dieses Werk wurde im Jahr 2013 vom Verlag Zeitschrift für Naturforschung in Zusammenarbeit mit der Max-Planck-Gesellschaft zur Förderung der Wissenschaften e.v. digitalisiert und unter folgender Lizenz veröffentlicht: Creative Commons Namensnennung-Keine Bearbeitung 3.0 Deutschland Lizenz. Zum ist eine Anpassung der Lizenzbedingungen (Entfall der Creative Commons Lizenzbedingung Keine Bearbeitung ) beabsichtigt, um eine Nachnutzung auch im Rahmen zukünftiger wissenschaftlicher Nutzungsformen zu ermöglichen. This work has been digitalized and published in 2013 by Verlag Zeitschrift für Naturforschung in cooperation with the Max Planck Society for the Advancement of Science under a Creative Commons Attribution-NoDerivs 3.0 Germany License. On it is planned to change the License Conditions (the removal of the Creative Commons License condition no derivative works ). This is to allow reuse in the area of future scientific usage.

2 928 Notizen range 2.2 plus a xa 2 separation, data collected/ unique/used 2181*. Three standard reflections m onitored every 97 reflections showed less than 3% variation and no system atic decay. L orentz, polarization and ab sorption correction were applied using Crystal Logic Software. The structures were solved by P atterson m ethods using SH ELX S-86 [13] and re fined by full-matrix least-squares technique with SH ELXL-93 [14]. H ydrogen atom s were not located. All non/hydrogen atom s were refined anisotropically. Optical absorption spectra were recorded by a Varian m odel 2390 spectrom eter. Preparation o f com poun ds [H3N (C H 2)6N H 3]I2, [H3N (C H 2)6N H 3]Br2 and [H3N (C H 2)6N H 3]C12 w ere prepared by treating H 2N (C H 2)6N H 2' with H I, H B r and HC1, respectively, evaporation of the solvent on a w ater bath and recrystallization from C H 3CN. [H3N (C H 2)6N H 3]BiI5 was prepared as follows. (B i0 )2C 0 3 (254 mg, 0.5 mmol) was treated with aq. HI (8 ml, 57% ) and then a solution of [H3N (C H 2)6N H 3]I2 (372 mg, 1 mmol) in aq. H I (4 ml, 57% ) was added at ca. 100 C. The solution was cooled slowly to room tem perature. The p re cipitate was filtered and washed with aq. HI. Recrystallization from hot aq. H I and slow cooling gave red-violet needles (yield 75% ); m.p.>300 C. * Crystallographic Inform ation files have been deposited in the Cam bridge C rystallographic D ata Center. D eposition num bers , , , for [H3N (C H 2)6N H 3]BiI5, [H3N (C H 2)6N H 3]BiCl5, [H 3N (C H 2)6N H 3]SbI5, and for [H3N (C H 2)6N H 3]SbBr5, respectively. H 3N (C H 2)6N H 3]BiCl5 was prepared by the same m ethod using (B io )2C Ö 3, HC1 and [H3N (C H 2)6N H 3]C12; white needles (yield 70% ); m.p.>300 C. [H3N (C H 2)6N H 3]SbI5 was prepared as follows. Sb20 3 (145.7 mg, 0.5 mmol) was treated with aq. H I (8 ml, 57% ) and then a solution of [H3N (C H 2)6N H 3]I2 (372 mg, 1 mmol) in aq. H I (2 ml, 57% ) was added at ca. 100 C. The solution was cooled slowly to room tem perature. The p re cipitate was filtered and washed with aq. HI. Recrystallization from hot aq. HI and slow cooling gave dark red needles (yield 80% ); m.p.= 250 C(dec.). [H3N (C H 2)6N H 3]SbBr5 was p repared by the same m ethod using Sb20 3, H B r and [H3N (C H 2)6N H 3]Br2; yellow needles (yield 85% ); m.p.>300 C. The com pounds [H3N (C H 2)6N H 3]xBiBr3+x and [H3N (C H 2)6N H 3]xSbCl3+x as well as similar com pounds with the amines H 3N (C H 2)2N H 3, H 3N (C H 2)3N H 3, H 3N (C H 2)4N H 3, H 3N (C H 2) i0n H 3, H 3N (C H 2)12N H 3, were also p repared but not in a good single crystal form [5]. Satisfactory analyses have been obtained for all new com pounds [5], Results and Discussion M orph ology o f materials The com pounds studied herein were prepared in pure form as single crystals. N eedle- shaped crystals w ere large enough for X-ray crystal structure determ inations and investigation of physical properties. Crystal structures A summary of crystal data of the com pounds [H3N (C H 2)6N H 3]BiI5, [H3N (C H 2)6N H 3]BiCl5, Table I. Summ ary of crystal, intensity collection and refinem ent data. Com pound [H3N (C H 2)6N H 3]BiI5 [H 3N (C H 2)6N H 3]BiCl5 [H3N (C H 2)6N H 3]SbI5 [H3N (C H 2)6N H 3]SbBr5 fw o a (Ä ) (5) (9) (8) (8) b ( A ) 8.661(3) 7.776(4) (6) 8.047(5) c ( A) (4) 19.97(1) (8) (9) V (A 3) (11) 3142(3) 1856(2) 1671(2) ß (deg) 92.36(1) Z Dcalcd/Dm e 3.384/ / / /2.51 asd Mg m -3 Space group Pn2ja P2,/n Pn2]a Pn2[a G O F R {/wr / / / /0.1242

3 Notizen P 4 P - l>» T S» T S Fig. 1. Crystal structure of [H3N (C H 2)6N H 3]BiI5 (a) along the 6-axis, (b) along the a-axis; only the inorganic chains (Bi-I net) are shown in diagram (b). H 3N (C H 2)6N H 3]SbI5 and [H3N (C H 2)6N H 3]SbBr5 at room tem perature is given in Table I. The packing diagram of [FI3N (C H 2)6NIT3]B il5 is shown in Fig. 1. The com pounds [H3N (C H 2)6N H 3]SbI5 and [H3N (C H 2)6N H 3]SbBr5, are isostructural with [H3N (C H 2)6N H 3]BiI5. The crystal structure of [H3N (C H 2)6N H 3]BiCl5 is shown in Fig. 2. The positional and equivalent therm al param eters of the non-h atom s and the bond lengths and angles of [H3N (C H 2)6N H 3]BiI5 are given in Tables II and III. Two general com m ents can be m ade which apply to all these structures as well as those of reference [6], Table II. Positional (xlo4) and equivalent therm al param eters (xlo3) of the non-h atoms, for [H3N (C H 2)6NH3]BiI5. E.s.d. s in parentheses. U (eq) is defined as one third of the trace of the orthogonalized Uij tensor. A tom X y z U (eq) B i(l) 8878(1) 10090(1) 8803(1) 29(1) 1(1) 7602(1) 10011(1) 10453(1) 45(1) 1(2) 10431(1) 9902(1) 7408(1) 44(1) 1(3) 8056(1) 7288(1) 8009(1) 49(1) 1(4) 7980(1) 12454(1) 7715(1) 47(1) 1(5) 10144(1) 7977(1) 10171(1) 39(1) N (l) 3042(6) 5838(11) 4377(7) 56(2) C (l) 2426(8) 4581(12) 4555(9) 55(3) C(2) 1542(7) 5067(17) 4874(7) 50(2) C(3) 983(8) 3737(14) 5189(8) 55(3) C(4) 71(8) 4190(16) 5516(8) 61(3) C(5) 57(7) 5291(15) 6346(7) 49(3) C(6) 559(10) 4693(14) 7176(7) 62(3) N(2) 456(8) 5792(12) 7977(7) 66(3) Fig. 2. Crystal structure of [H3N (C H 2)6N H 3]BiCl5. All com pounds have ID inorganic network. They consist of corner-sharing M X6~ distorted octahedra which form, via cis halogen bridges, zigzag anionic chains. O rganic cations fill the space betw een the chains preventing them from interacting which results in the ID character of these com pounds. There are three distinct pairs of M-X bonds: bridging, term inal trans to bridging and term inal cis to the bridging. In the ideal case each pair of bonds would have equal lengths. This is not the case here, but we do observe the expected ord ering of bond lengths: bridging>cis>trans.

4 930 Notizen Table III. Bond lengths [A] and angles [dee], for [H3N(CH2)6NH3]BiI5. Bi(l)-I(4) 2.914(1) I(4)-Bi(l)-I(3) 99.93(3) Bi(l)-I(3) 2.957(1) I(4)-B i(l)-i(l) 97.78(3) B i(l)-i(l) 3.062(1) I(3)-Bi( 1 )-I( 1) 90.81(3) Bi(l)-I(2) 3.098(1) I(4)-Bi(l )-I(2) 92.59(3) Bi(l)-I(5)#l 3.260(1) I(3)-Bi( 1 )-I(2) 91.60(3) Bi(l)-I(5) 3.301(1) 1(1 )-Bi( 1 )-I(2) (2) 1(5 )-Bi( 1 )# (1) I(4)-Bi(l)-I(5)#l 85.19(3) N (l)-c (l) 1.457(14) I(3)-Bi(l)-I(5)#l (2) C(l)-C(2) 1.48(2) I(l)-B i(l)-i(5)#l 87.39(3) C(2)-C(3) 1.50(2) I(2)-Bi(l)-I(5)#l 89.25(3) C(3)-C(4) 1.51(2) I(4)-Bi(l)-I(5) (2) C(4)-C(5) 1.53(2) I(3)-Bi( 1 )-I(5) 91.17(3) C(5)-C(6) 1.51(2) 1(1 )-Bi( 1 )-I(5) 83.96(3) C(6)-N(2) 1.502(14) I(2)-Bi(l)-I(5) 85.05(3) I(5)#l-B i(l)-i(5) 83.76(3) Bi(l)#2-I(5)-Bi(l) (2) N (l)-c (l)-c (2) 115.0(10) C(l)-C(2)-C(3) ( 1 1 ) C(2)-C(3)-C(4) 114.3(11) C(3)-C(4)-C(5) 114.7(10) C(6)-C(5)-C(4) 113.4(10) N(2)-C(6)-C(5) 109.6(10) Symmetry transformations used to generate equivalent atoms: #1 -x+2, y+112, ~z+2; #2 -x+2, y-1/2, -z+ 2. O ptical properties Fig. 3 shows the room tem p erature optical absorption spectra of thin deposits [15] of [H3N (C H 2)6N H 3]BiI5, and Wavelength (nm) Fig. 3. Optical absorption spectra of thin deposits of [H3N(CH2)6NH3]BiI5 (a) and [H3N(CH2)6NH3]BiCl5 (b) at room temperature. Wavelength (nm) Fig. 4. Optical absorption spectra of thin deposits of [H3N(CH2)6NH3]SbI5 (a) and [H3N(CH2)6NH3]SbBr5 (b) at room temperature. [H3N (C H 2)6N H 3]BiCl5, while Fig. 4 shows the room tem perature optical absorption spectra of thin deposits of [H3N (C H 2)6NH3]SbI5, and [H3N (C H 2)6N H 3]SbBr5. The excitonic-peak position of [H3N (C H 2)6N H 3]BiI5 occurs at ca. 554 nm (2.24 ev). The excitonic-peak position of A 3BiI6 (0D) occurs at ca. 474 nm (2.62 ev) and that of B il3 (q- 2D) at ca. 603 nm (2.05 ev) [1-4,16]. It appears that the excitonic binding energy of [H3N (C H 2)6N H 3]BiI5 is ca. 242 mev, i.e., m ore than twice the binding energy of B il3, (ca. 100 mev). Similar results were obtained for other ID systems [H3N (C H 2)6N H 3]BiCl5, [H3N (C H 2)6N H 3]SbI5, [H3N (C H 2)6N H 3]SbBr5 (Figs. 3, 4). However, the excitonic binding energy of antim onates is sm aller than that of the corresponding bism uthates (for Sbl3 see [17]). In all cases the excitonic absorption band is shifted to lower energies and the excitonic binding energy becomes smaller as the dim ensionality increases. As in the cases of Pb and Sn based systems [7-10], it is expected that the peak position of M X41_ (2D systems based on Bi and Sb) should occur at lower energies than those of M X52~, namely, close to those of M X3 (q-2d) systems; but such com pounds have not been prepared yet.

5 Notizen 931 [1] G. C. Papavassiliou, G. A. Mousdis, I. B. Koutselas, C. P. R aptopoulou, A. Terzis, M. C. Kanatzidis, A. Axtell III, Adv. M ater. O pt. Electron., in press (1998). [2] T. Kawai, S. Shim anuki, Phys. Stat. Sol. 177b, K43 (1993). [3] G. C. Papavassiliou, I. B. Koutselas, Z. N aturforsch. 49b, 849 (1994). [4] G. C. Papavassiliou, I. B. Koutselas, A. Terzis, C. P. R aptopoulou Z. N aturforsch. 50b, 1566 (1995) and refs cited therein. [5] G. C. Papavassiliou, G. A. M ousdis unpublished work. [6] J. Zaleski, A. Pietrasko, J. Molec. Struct (1994); G. C. Allen, R. F. M cmeeking, Inorg. Chim. A cta, (1977); W. G. M cpherson, E. Meyers, J. Phys. Chem (1968). [7] G. C. Papavassiliou, A. P. Patsis, D. J. Lagouvardos, I. B. Koutselas, Synth. M etals 57, 3889 (1993). [8] G. C. Papavassiliou, Mol. Cryst. Liq. Cryst. 286, 231 (1996). [9] T. Ishihara J. Lumin (1994). 10] G. C. Papavassiliou, Progr. Sol. State Chem. 25, 125 (1997). 11] S. Wang, D. B. Mitzi, G. A. Landrum, H. G enin, R. H offm ann, J. Am. Chem. Soc. 119, 724 (1997); D. B. Mitzi, Inorg. Chem. 35, 7614 (1996). 12] Crystal Logic Inc., W. Pico Blvd., Suite 106, Los Angeles, CA ] G. M. Sheldrick, SHELXS 86, Structure Solving Program, University of G oettingen, G erm any (1986). 14] G. M. Sheldrick, SH ELX L 93, Crystal Structure R e finem ent, University of G oettingen, G erm any (1993). 15] For the m ethod of thin deposits preparation see refs 3,4,7. 16] A. D. Brothers, D. M. Wielczka, Phys. Stat. Sol. 80, 201 (1977). 17] Y. Kaitu, T. Komatsu, T. Aikami, Nuovo Cim ento 338, 449 (1977).

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